Papers by Author: Sheng Li Ma

Abstract: Zirconia (ZrO2) films were deposited by metal-organic chemical vapor deposition (MOCVD) on {1 0 0} Si single crystal using Zr(thd)4 precursors. The thickness of obtained films is typically of 3.5 μm. The samples have been characterized by Field-Emission-Gun Scanning Electron Microscopy (FEG-SEM) for morphologic and microstructure study, and by X-ray Diffraction (XRD) for crystalline structure. The microstructure analysis showed that unexpected stable single tetragonal phase preferentially grew in low temperature area. According to the literature, the tetragonal phase stabilization is related to the crystalline size and the internal compressive stress. To analyze the effect of grain size and internal stress on the phase transformation, the thermal annealing were carried out in different temperatures and internal stress was measured by XRD method.

Abstract: Series Ti-Si-C-N coatings with different carbon were deposited on a high-speed-steel substrate by means of pulsed direct current plasma enhanced chemical vapor deposition (PECVD). The structure and hardness were subsequently investigated using X-ray diffraction, transmission electron microscopy and microindentation measurements. It was found that the carbon content had a profound effect on the microstructure and hardness of the Ti-Si-C-N coatings. The results indicated that these coatings consisted of the dominant nanocrystalline Ti(C, N), accompanying with a small amount of silicide (TiSi2, Si3N4 or SiC) dispersed within the dominant phase. An increase in C content resulted in the decrease in the grain size and the increase in fcc-structure lattice parameter. A maximum hardness of 48 GPa was achieved for a two-phase {Ti (C N) + SiC} structure at the C content of 38.6 at.%.